1. Field of the Invention
The invention relates generally to a method and device for controlling the impingement of the workpiece by a water jet or an abrasive water jet in a cutting unit.
2. Background and Related Information
Units in which a thin water jet strikes a workpiece at high speed and with high energy so as to cut and/or sever the workpiece with a relative motion, so as to cut the workpiece, are generally known in the field. In addition, water alone, or water and particles that have an abrasive effect and are carried along therein, can also be used to cut and/or sever workpieces.
Water jet or abrasive water jet devices are essentially used to cut out desired shapes from optionally hard and/or brittle flat workpieces. Precise contours are advantageously produced from glass areas, e.g., panes, e.g., by way of abrasive water cutting units.
In some water jet cutters, if a cut is created in cutting units through relative guidance of the cutting jet from outside into a flat workpiece, this jet can be embodied with a high pressure and high speed or energy necessary for a high cutting power.
In many cases, workpieces of a flat raw material of oversized production can also be cut out by way of a water jet or abrasive water jet method, whereby either a cut can be created starting from the edge, or a through hole is first made in the material surface or material wall, starting from which hole the penetrating jet is effective in producing a cut with relative motion.
With brittle materials, such as, for example, glass or the like, creating a hole through the raw material wall is often difficult because the abrasive water jet has a high impact pressure that can lead to the destruction or fracture of the raw material.
In order to minimize this danger when placing a through hole, also referred to as “piercing,” the cutting jet directed at the surface until penetration through the material wall is usually embodied with reduced energy or reduced pressure, after which a substantial increase in pressure occurs to actually create a cut.
Typical formation of a through hole is made in a raw material wall with reduced pressure application, after which an increase in pressure of the jet medium occurs and a cut is produced through targeted relative motion between raw material and jet nozzle, and further includes a switch-over action of the nozzle impingement. However, the conventional methods and devices which include a switch-on and switch-over action of this type with pressures in the medium of up to 450 MPa can be time-consuming and/or subject the unit parts to considerable wear.